An organic electroluminescence device (hereinafter, “electroluminescence” may be abbreviated as “EL”) is a spontaneous light emitting device which utilizes the principle that a fluorescent substance emits light by energy of recombination of holes injected from an anode layer and electrons injected from a cathode layer when an electric field is applied.
The organic EL device has a light emitting layer between the anode layer and the cathode layer, and an electron can be efficiently injected and transported by providing an electron injection region such as an electron injecting layer or an electron transporting layer between the light emitting layer and the cathode layer. A large number of researches have been heretofore conducted on the electron injection region with a view to improving the efficiency with which an electron is injected or transported and the heat resistance of the organic EL device. Given as a method of improving the efficiency with which an electron is injected or transported is, for example, a method involving using an extremely thin alkali metal oxide or alkali metal halide in the electron injecting layer (see Patent Literatures 1 and 2), a method involving using a co-deposited layer of a transition metal oxide and an alkali metal halide as the electron injecting layer (see Patent Literature 3), a method involving using the electron injecting layer containing a conductive metal oxide such as molybdenum oxide and an alkali metal (see Patent Literature 4), or a method involving laminating a transition metal oxide layer and an alkali metal or alkaline earth metal layer to provide the electron injecting layer (see Patent Literature 5).